Quinolone derivatives were initially discovered as the agents to act on bacterial DNA gyrase, and thus developed as anti-bacterial agents. Recently DNA topoisomerase II has emerged as the pharmacological target for this class of quinolone compounds. We have synthesized a series of substituted 2-phenyl-4-quinolone (A) which appeared to function as novel antimitotic agents. [Kuo, S. C., Lee, H. Z., Juang, J. P., Lin, Y. T., Wu, T. S., Chang, J. J., Lednicer, D., Paull, K. D., Lin, C. M., Hamel, E. Synthesis and cytotoxicity of 1,6,7,8-substituted 2-(4′-substituted phenyl)-4-quinolones and related compounds: identification as antimitotic agents interacting with tubulin. J. Med. Chem. 1993, 36, 1146-56; Li, L., Wang, H. K., Kuo, S. C., Wu, T. S., Mauger, A., Lin. C. M., Hamel, E. Lee, K. H. Antitumor agents. 155. Synthesis and biological evaluation of 3′,6,7-substituted 2-phenyl-4-quinolones as antimicrotubule agents. J. Med. Chem. 1994, 37, 3400-7] Later on we continued to synthesize many related analogs such as 2-phenylnaphthyridine-4-ones (B) [Chen, K., Kuo, S. C., Hsieh, M. C., Mauger, S A., Lin, C. M., Hamel, E., Lee, K. H. Antitumor agents. 174. 2′,3′,4′,5,6,7-Substituted 2-phenyl-1,8-naphthyridin-4-ones: their synthesis, cytotoxicity, and inhibition of tubulin polymerization. J. Med. Chem. 1997, 40, 2266-75], 2-phenyl-4-quinazolones (C) [Xia, Y., Yang, Z. Y., Hour, M. J., Kuo, S. C., Xia, P., Bastow, K. F., Nakanishi, Y., Namrpoothiri, P., Hackl, T., Hamel, E., Lee, K. H. Antitumor Agents. Part 204: Synthesis and Biological Evaluation of Substituted 2-Aryl Quinazolinones, Bioorg. Med. Chem. Lett. 2001, 11, 1193-6; Hour, M. J., Huang, L. J., Kuo, S. C., Xia, Y., Bastow, K. F., Nakanishi, Y., Hamel, E., Lee, K. H. 6-Alkylamino- and 2,3-dihydro-3′-methoxy-2-phenyl-4-quinazolinones and related compounds: their synthesis, cytotoxicity, and inhibition of tubulin polymerization. J. Med. Chem. 2000, 43, 4479-87] and tetrahydro-2-phenyl-4-quinolones (D) [Xia, Y., Yang, Z. Y., Xia, P., Bastow, K. F., Tachibana, Y., Kuo, S. C., Hamel, E., Hackl. T., Lee, K. H. Antitumor agents. 181. Synthesis and biological evaluation of 6,7,2′,3′,4′-substituted-1,2,3,4-tetrahydro-2-phenyl-4-quinolones as a new class of antimitotic antitumor agents. J. Med. Chem. 1998, 41. 1155-62], which enable us to establish structure and activity relationships (SAR). Among these analogs, we have discovered quite a few compounds possessing potent cytotoxicity, such as 3′,6-disubstitued 2-phenyl-4-quinolones (A-1) etc [Li, L., Wang, H. K., Kuo, S. C., Wu, T. S., Lednicer, D., Lin, C. M., Hamel, E., Lee, K. H. Antitumor agents. 150. 2′,3′,4′,5′,5,6,7-substituted 2-phenyl-4-quinolones and related compounds: their synthesis, cytotoxicity, and inhibition of tubulin polymerization. J. Med. Chem. 1994, 37, 1126-35]. However, most of the compounds with potent cytotoxicity were very lipophilic, and therefore, not suitable for in vivo and clinical studies. We thus made attempt to introduce carboxylic acid group on the 2-phenyl-4-quinolone skelecton in order to improve pharmacokinetic properties suitable for in vivo and clinical studies. 